This invention relates to an electronic component with a soldering-less terminal structure, and more particularly to an electronic component with a terminal connection structure which carries out connection without soldering.
Use of freon is subject to restriction in view of environmental pollution, so that it is highly required to connect a terminal conductor, a lead wire or the like to a connection electrode of a circuit board without soldering. This is likewise true of an electronic component called a focus pack used for adjusting a focus voltage of a cathode ray tube, a screen voltage thereof or the like.
U.S. Pat. No. 4,471,339 teaches a high-voltage variable resistor including a terminal connection structure for connecting, by means of a terminal fitment like a coiled spring provided at one end thereof with a ring into which a connection conductor or connection terminal is inserted, a connection electrode of the resistor to the connection terminal without soldering. Such a conventional terminal fitment as disclosed in the U.S. patent fails to firmly hold the connection terminal therein, to thereby cause the connection terminal to be easily released from the terminal fitment. Also, it tends to cause a failure in electrical connection to occur between the connection terminal and the terminal fitment. Further, the above-described construction of the terminal fitment requires to keep the connection terminal and connection electrode connected together prior to reception of a circuit board in an insulating casing. This, when a lead wire of an increased length is required for the connection conductor, causes the long lead wire to obstruct assembling of the high-voltage variable resistor. In particular, when the high-voltage variable resistor including the terminal connection structure is combined with a fly-back transformer, the high-voltage variable resistor must be placed in a heating oven together with the long lead wire for the purpose of subjecting a resin material for molding the fly-back transformer heat curing. Unfortunately, the long lead wire renders the operation highly troublesome and and deteriorates production efficiency.
In order to solve the problem, the assignee proposed a terminal connection structure for connecting a core of a lead wire to a connection electrode of a circuit board without soldering, as suggested in Japanese Utility Model Application No. 87639/1992 and U.S. patent application Ser. No. 158,943 corresponding thereto. The terminal connection structure is constructed in such a manner as shown in FIG. 9. More specifically, in FIG. 9, reference numeral 101 designates a circuit board on which a resistance circuit pattern and a plurality of connection electrodes are provided. The circuit board is received in a board receiving section of an insulating casing 102 made of insulating resin. The substrate receiving section of the insulating casing 102 is provided on an inner periphery thereof with a board fixing rib 103 for supporting the circuit board 101 in a manner to form a space between a front surface of the circuit board and an inner surface of the insulating casing 102. The circuit board 101 is adhered to the rib 103. The insulating casing 102 is formed therein with a terminal fitment fit section 104, in which a terminal fitment 105 and a conductive rubber member 106 are received. The conductive rubber member 104 functions as a connection means for connecting a connection electrode 107 arranged on the circuit board 101 and the terminal fitment 105 to each other without soldering. The terminal fitment 105 includes a connection conductor holding section 105b provided with a plurality of edges 105a which are adapted to bite into an outer periphery of an end of a core of a lead wire 109 inserted into the insulating casing 102 via a through-hole 108 of the casing 102. The terminal fitment 105 further includes four walls 105c arranged on sides of the connection conductor holding section 105b so as to extend in a direction of insertion of the lead wire 109 perpendicular to the connection conductor holding section 105b, respectively. Of four such walls 105c, the wall 105 contacted with the conductive rubber member 106 is provided on an outer surface thereof with a projection 105d, which is then inserted into a through-hole 106a of the conductive rubber member 106.
As will be noted from the foregoing, the proposed terminal connection structure thus constructed requires the conductive rubber member 106 in addition to the terminal fitment 105, to thereby increase both the number of parts required for the structure and the number of steps required for the assembling. Also, the conductive rubber member is relatively expensive, leading to an increase in cost of an electronic component or a high-voltage electronic component such as a high-voltage variable resistor or the like.
A structure for connecting the connection conductor and the terminal fitment to each other is disclosed by way of example in Japanese Utility Model Application Laid-Open publication No. 192601/1987 and U.S. Pat. No. 4,834,603 and the like.